1. Field of the Invention
The present invention relates to a fixed construction for plate electrodes in a flat display unit for an image producing apparatus.
2. Description of the Prior Art
In recent years, flat display units for displaying a colored television image have come into the spotlight. As illustrated in FIG. 12, the flat display unit displays a colored television image by focusing and deflecting electron beams emitted from electron beam sources 1 in both the horizontal and vertical directions using a plurality of plate electrodes 3, the electron beams landing on phosphors coated on each cell 4 of a screen 5.
In such flat display units, as shown in FIG. 13, a spacer c the insulating surfaces of which are coated with bonding glass b having a low melting point has previously been used, which is disposed between the above mentioned plate electrodes a to fix them accurately in position with a specified spacing provided therebetween and in an insulating manner from each other, the spacer c being heated, under pressure, up to the melting point (usually, approximately 500.degree. C.) of the glass b to fix the plate electrodes a in position with the spacer c interposed therebetween. However, this conventional technique has had the problem that the heat causes oxidation and thermal deformation of the plate electrodes a, resulting in misalignment of landing areas of the electron beams, so that the picture quality will be substantially degraded.
To overcome the above problem with the prior art, the inventors of the present invention have proposed in their previous application a technique in which tapered insulating pins are press-fitted into holes formed in the plate electrodes which are disposed with a specified spacing provided therebetween, thereby supporting and fixing the plate electrodes in position with the specified spacing provided therebetween without interposing the spacer c (FIG. 13) as required in the prior art and without requiring heating.
However, the above-proposed previous technique has had the shortcoming that since the areas around the peripheries of the holes of the plate electrodes become deformed when the insulating pins are press fitted into the holes, the dimensional accuracy provided between the plate electrodes tends to deteriorate, resulting in misalignment of the landing areas of the electron beams and hence, degradation of the picture quality.
The previously proposed technique has had the further shortcoming that since sliding friction is caused between the insulating pins and the peripheral portions of the holes of the plate electrodes when press-fitting the insulating pins, metal powder shaved off the peripheral portions tends to adhere to the surface of the insulating pins, thus leading to shorting between the plate electrodes, and also the supporting strength of the insulating pins tends to be deteriorated because of flaws caused to the surface thereof, resulting in the deterioration of the pressure-withstanding strength of the plate electrodes.